Safety release system for drilling machines and the like



July 7 1959 F. c. G. BERTHIEZ 2,893,273

SAFETY RELEASE SYSTEM FOR DRILLING MACHINES AND THE LIKE July 7, 1959 F. c. G. BERTHlEz 2,893,273

SAFETY RELEASE SYSTEM EOE DRILLING MACHINES AND THE LIKE Filed Sept. 9, 1957 I5 Sheets-Sheet 2 3] 2f' a? 7 3,/ a g4 I8 4 1 Y! L? 4F' f6 l 2 3 gg l 35 1f .f5 d I, 19 29 l lill Il l 2 23 f4 NvENToR 'Frelev'wk Chan-RS Gr verf BerHnie-L ATTORNEY July 7, v1959 F. c. G. BERTHIEZ 2,893,273 l SAFETY RELEASE SYSTEM FOR DRILLING MACHINES AND THE LIKE Filed Sept. 9. 195'?` 5 Sheets-Sheet 3 Q .ms lf w G WN NN mM,

m Y di I EL.

INVENTOR Fvederick Charles United Patent essisnor .t Societe Andiamo der, Aneiens Etablisseatente @alla tertiaire a Frears of.4 Application September 9, 19751,' Serial N o,- 682,915,

1e clams.. (el. nasi- 11.

This invention relates. to Safety,i release systems forma.- ehinentools, andy phrtieularly to safety release systems ap.- plicable to drilling machines andthe like, Abasic object of the invention is to impart to. the drill carrier. of` a drillinsmachine Positive, instantaneous backing movement away from the work whenever the d rilling resistance attains a predetermined high value.

In drilling operations a high axial thrust is imposed o n tha-drill bit. This thrust retains a substantiallyuniform value in Steady. operation provided the metal being worked has uniform characteristics. For various. accidental causes however., suchy as a hard area in the WOrkor faulty discharge of the cuttings from. the holeA beingdril-led, the axial thrust developed at the drill carrier. or; drill bar may suddenly jump to an abnormally high` value', for. example, twoormore times its normal rated value; A lsoin cases where the drill tool is poorly sharpened, chipped or` other- Wise faulty. the drilling. thrust may attainvalues substantially. in excess of normal. All such circumstances` generally, result in breaking the0 drilling tool, and this. not only involves replacement of valuable. tools, but costs m'oney in machine shut-down time. Various forms ofV safety release, systems. have. been devised for. arresti-ng, the feed of the; tool towards the work whenever a predetermined high reaction pressure develops in a drilling operation, as byfdisengaging aclutch interposed between the drill carrier. and the'feed motor or. other power means driving. it. In conventional sys# tems, o f.- this kind, thel tool; carrier. usually remains at the position it reached by the time the safety. system operated, or a short time after, sol that the. continuedlrotation: ofthe World relatively l0. a. stationary. tool results in an abnormal glazed ySurface. condition being. imparted to the.' work which'fis especially objectionable when the work comprises stainless. steel and/ormanganese. alloy steels. Moreover, the disengagement of' the clutch between the drillf carrier and feed motoris not instantaneousso that. the drill generallfy continues toprogress for a time. after. the abnormal pressure has developed.

In some types of drilling). machines the. drill'carrier. is

moved over. guideways by` means of; an hydraulic ram motor or. the like.. When an abnormalincrcase in drilling reaction pressure occurs, a pressure surgeis. created in' the operation chamber ofl the. ram cylinder and this. pressure, surge rst is use d to, arrest'the application off feed power. from the ram to. the drillcartier, and then to reverse,r the direction of. operation of. the ram.v This action however, owingv to; the inherent elasticity. of.' the larg@ column of hydraulic 'uid contained in the rain cylinder and piping, andV also due tounavoidable pressure losses in the hydraulic circuit, is comparatively sluggish. The over-allt time,r constantofsuch a system, including the individual constants of the. hydraulicv components such as servo-valves, electromechanical relays and the: like, has

anorder. of. magnitude of aboutone second. Assuming an average drilling rotational speed of 40 revolutionsper' second, it is thus1 seen that the, work willi, have revolved about forty times from the time the objectionable increase in drilling-pressure has occurred and before the drill feed displacement'has been reversed. By that time there is every likelihood for the drill bit to break.

It is an object of the invention to. provide a safetyl system of the. type'described wherein the time constant, VLe. the time. lapse from. the instant an abnormally high drilling reaction pressure is reachehd to the instant the tool is backed away. from the work, isv greatly reduced as. compared to what was. heretofore found possible; and specifically, to provide such a system wherein such over-all time constant-is so short (eg. of the. order of: one fourtieth of a second) that theV tool will not have time to` rotate more. than once or. twice before it. is positively. backed olf, thereby. greatly.' reducing the. likelihood of: damage to the tool and work.

Another. object is to. provide such a system wherein effective use isv made of the high reaction pressure gener.- ated bythe machining resistance, in 'order to impart a more positive and swift backing movement to the tool away from the work or of the work from the tool.

According to an aspect of the'invention, the increased drilling resistance is sensed by a deformable element, such as a iuid pressure capsule, and deformation of this element. in vresponse to the mechanical pressure of the drilling operation, is used to actuate a device for releasing potential energy stored, eg. in a spring, the release of this stored energy serving to impart the'ba'cking movement' to the tool. v

There is thus provided, in accordance with the inventiori, 4al' safety. release device for amachine-tool having coacting tool and work-carrying elements and feed means for moving said elements towards each other iri opposition to machining resistance, which device includes means for storing potential energy, means 'operated by the release of said energy for imparting to said elements a highvelocity positive' movement' away" from each other, means such as a latch normally preventing the release of`said energy;A andV pressure-responsive means actuated by a predetermined high degree of pressure generated by lsaid machining resistance for disabling said release-preventing means. i Thus. the mechanical time constant of the system may be substantiallyreduced to the mere/'time required for the retraction o'fa suitable latch. rlhe latch may be held in its normal release preventing position by. an electromagnet against the action of a spring,` Wherebythe time lapse required for initiating the toolV backing movementv will practically depend onlyupon the` degree of acceleration obtainable with the latch" bias spring and the. energy-storage spring. Consequently," even if vthe disengagement ofthe feed motor clutch is not instantaneous, the backing of the tool/carrier element or drill bar will effectively. insure an instantaneous retraction of the tool (eg. drill bit) from its dangerous position in the work.`

The energy-storing means is preferably provided in the form of a compression springa'cting between the feed carriage and the drill bar. l WSince the thrust forces involved between the drill and the 'workpiece` are high, e.g`. of the order ofone ton, suitable device v-for releasing a latch under such higli forces "raises a number of problems, and further objects of the invention lie in solving these problems. Thijs, according to a feature of` the invention, the arrangement issuch thatthe latch does not have to exert substantially' any restraining force on the drillV bar in an axialA dire'c tion parallel to the feed? movement. For this purpose to.' reduce substantially the tangential forces 'generated by the axial thrust of the energy-storing spring. The

latch therefore, in such an arrangement, is simply required to be so mounted pivotally n the carriage as to oppose the purely rotational component of the helical motion of the bar, in order to block the bar positively vagainst any relative displacement with respect to the feed carriage so long as the spring pressure acting parallel to the feeding movement has not been exceeded by the drilling reaction pressure.

The pressure-responsive element sensing the drilling reaction pressure as transmitted through the drill bar, and the energy-storing spring, are preferably arranged coaxially so as to act on the bar in opposite directions at aligned points of said bar structure, and the aforementioned means constraining the bar to describe a helical path relative to the carriage may comprise mating, inclined surfaces on a cam follower carried by the bar and on the pressure-responsive element, the area of engagement of said inclined surfaces also lying on the common line between said pressure responsive element and spring. Said mating inclined surfaces may be formed, respectively, on a lateral extension unitary with the drill bar, and on the adjacent end of a plunger the other end of which engages the pressure-responsive capsule.

According to a further feature `of the invention, resetting means are provided, e.g. in the form of a manual lever which serves lirst to restore the bar to its operative position in opposition to the energy-storing spring, and thereafter acts to recondition the electromagnetic means actuating the latch.

An exemplary form of embodiment of the invention will now be described by way of illustration but not of limitation with reference to the accompanying, somewhat diagrammatic, drawings, wherein:

Fig. 1 is a vertical cross sectional view of a drill feed carriage;

Fig. 2 is a horizontal section on the line II--II of Fig. 3, and

Fig. 3 is a vertical cross section on the line III- III of Figs. 2 and 4.

Fig. 4 is a plan view of a machine tool embodying the safety release device of the invention.

As shown in the drawings, an improved drilling assembly comprises an under frame formed with longitudinal slideways 1 (see Fig. 3), upon which is longitudinally slidable a base 2 forming part of a carriage including the casing 3 mounted on said base. A tubular sleeve 4 isjournalled in bearings, not shown, near the top centre of the casing 3 for limited rotation and axial movement and is retained by one or more arcuate cover plates such as 6. Secured in the sleeve 4 coaxially with it is the drill bar or rod 5, which carries a drill, not shown, on its end positioned forwardly of the plane of the drawing in Fig. 1 or Fig. 3. The sleeve 4 is formed with a lateral extension or shoe 7 (see Figs. 1 and 2) serving as a cam follower to provide the kinematic connection between the carriage 2 and drill rod 5 as presently to be described.

In the plan view of the machine tool of Fig. 4 the base or carriage 2 slidable on the slideways 1 is moved along the slideways by means of a nut 51 carried by the base 2 in threaded relation to Vwhich a feed screw 53 extends horizontally parallel to the slideways and is rotated through an electromagnetic clutch 55 by motor 57 suitably supported on the under frame of the machine at the end of the slideways. The nut S1 and the feed screw 53 are shown in Fig. 3, supporting parts and bearings being omitted.

The work supporting member 59, also supported on the slideways 1, carries a rotatable member 61 rotatable on the horizontal axis in alignment with the drill bar 5 and driven by motor 63 through transmission 65. Section IIl-III in Fig. 4 is substantially the section shown in Fig. 3 of the drawings.

Fig. 2 being a plan view taken below the sleeve 4 and drill rod 5, the latter is not shown therein, but it will be understood that the extension or shoe 7 is adapted to move slightly in the direction indicated by arrows f1 and f2 in that gure, on rotation of the sleeve 4 with the drill rod. The arrow f3 indicates the direction towards that end of the drill rod carrying the drill, and likewise indicates the direction of feed of the drill rod during a drilling opeartion.

The shoe 7 is urged by a spring 13, presently to be described, in a direction indicated by the arrow f4, into engagement with the flat slanting end surface of a plunger 8 which is slidably mounted in a sleeve 9 integral with the casing 3. The opposite end of sleeve 9 is formed as a housing receiving a manometric capsule or pressureresponsive member 10 of any suitable description, engaged at one end by the adjacent end of the plunger 8, and at its other end connected by a pressure-transmitting line 11 with a pressure-responsive contact switch 12, Figs. l and 3, not shown in detail.

The biasing spring 13 is mounted between tapered end bearing studs 1S and 16, stud 15 being seated against a seat in member 14 secured in the casing 3, and stud 16 in a seat formed on the shoe 7.

It will be noted that owing to the engagement of the cam surface 17 provided on the shoe 7 with slanting surface on the end of plunger S, the axial thrust developed by spring 13 as indicated by arrow f4, results in a transverse force component on the shoe 7 in the direction indicated by arrow f1. Normally the shoe 7 is held by the action of this component against a detent latch member 18 secured to an arm 19 pivoted to the casing by means of a pivot shaft 20 journalled in ball bearings. Thus, as long as the arm 19 is positioned as indicated in Fig. 2, the shoe 7 is held in position for unitary movement with the carriage 2, being prevented from movement to the left in Fig. 2 by the latch member 18 and arm 19. As long as an excessive pressure is not developed in the pressure responsive member 10 under the resistance of the workpiece on which the drill presses, the shoe 7 is held by spring 13 and the engaged cam surface in abutment with the latch member 18, except insofar as such connection is able to yield slightly owing to the resiliency of spring 13 and flexibility of the pressure capsule 10 under varying reaction pressure of the workpiece. It is further noted that the rotary reaction exerted bythe work upon the drill tool carried by the drill rod S, likewise tends to rotate the shoe 7 in a direction the reverse from that indicated by arrow f5 in Fig. 3, so that such reaction in eiect contributes to applying the shoe 7 against detent member 18.

When the axial drilling force increases the plunger 8 exerts increased pressure upon the end wall of capsule 10; when this increased pressure has resulted in a small, predetermined amount of displacement of the capsule wall the pressure-responsive switch 12 is actuated. Through Vmeans later to be described, actuation 'of the switch 12 rotates the arm 19 in the direction shown by arrow F (counterclockwise) in Fig. 2 and the latch 18 is retracted from engagement with the shoe 7. The detent spring 13 then prevails to cause the drill bar 5 and shoe 7 to move slightly in the direction shown by arrow f1 by virtue of the engagement of the inclined surface 17 with the slanting end surface of the plunger 8. Actually, since the shoe 7 is rearwardly abutted against the plunger 8 which is practically stationary, the said movement of recession is accompanied by a rotation of the drill rod, the shoe being rotated in the direction indicated by arrow fl. During this rotation the angle of inclined plane 17 is altered, but the plunger 8 nevertheless remains at all times applied against the shoe on the plane 17, since said plunger is entirely Vfree to rotate on its axis within the sleeve 9. The rotation of shoe 7 thus eifected by the spring 13 brings it into engagement with an adjustable stop screw 21, and the concomitant rearward displacement of the shoe imparted to the drill rod is indicated in Fig. 2 as the displacement c.

Means will now be described for causing retraction of the f'detentflatch yL18:v underfcontrol of "the'pressure switch 12.- The arm 19 is biassed in the directionindieated'by farrov`v`1Fby af-springzl having one end-'connected to an n'adjustablylpositionedanchoring memberzfheld'by vthe wallolthecasingland'its other end connected to a bolt on 211111119. A3 link 2S l' is'c'onnected fat onesendV tothe movable armaturez lf -arsolenoid 27 and -hasits ops'positef-end pivotally cormectedv to thebolt "24. The sole- -noid 127 asf'shownin'Fig. 3 -is connected-byleads 70 to the switch'-12-whichlcontrols 'the'energization of this solevheid.

Spring '22 -and solenoid I2:7 'are arranged to'develop "forces lin l opposite directions, and `wher'rthe solenoid V27 iiseener'gized the force "developed -'byit 'predominates over ithe lfor'c'e `of 'thei-slnrir'vigZZ.y '"On deenergizaton of the --slenoid Ythe ispring 22 retractsthe7-a'rm f in "the `direction f-fr'rfOWF. i Y i' 4 i il i "liexible compression spring '28 having 'one Vend abutted against farm "19 vand its opposite Yend labutted 'fagaiustfthebaI-llike head r29 ofa pullerod 'extending through an aperture 3'1in` the YarmY v19, tends ,to 'displace fthe 1-9 in 'the direction indicated-by the arrow Ff. lAbushing yzlserves to support thespfring -23 and the rod "30 extending within the'bushingSZ-has' its vend 38 -remote {f rdm 'the head 2 9 pivote'd'- to Ya crankmember 45 .pro- '-vided on ashaft 33. This"'sha'ft yis'manually operable by means'of'a lever 34,.

Thev system operates as ifollows: PDuring a drilling"- opertion themovable'armature'.26 lis 'retracted intotheenergired :solenoid `27 as Ashown in --Fig.l2,'jthesit/ tch'l being closed under the vnormal p ressrein 'the capsulek 10;" The shoe-7 isthen blocked r`by l'atclli `Arrr-einher" '18. `When aJ pressurejsurge is transmitted 4to;'thepressure unit 10i upon backingm'oveme'nt ofthe rod 5, shoe 7 and plunger 8, due to excesrsivre'drilling resistance Tas previously described, switch '12,is opened and deenergizjes `"solenoidZL'and arm`19 is rotatedby spring @Z `in` the direction of arrow 24F, thereby disenga ging Vlatch :'I'8 froml Ashoe '7 -and allowing Athe/drill rod v5 to" rotate yreversely-`slightly,` that 'isjclockwise in Fig. 3 until the "7' 'abts "the stop 21'. "During this V,aotion the spring 28 is compressed but itis substantially weaker thanfspringiZZ 'so that n.tltleesplrirlg 28. doesnot interfere withthefinsttar'ieous'retractionioflatch '118 by the spring "."After the safety release Adevice has operated in the `marmerjust described, the 'operator resets `the mechanism f'afndeanmesurnedrillingoperations after rst, 4of course, jliavirifg'deterrninedgu'lfd cre'd "the source of Atrouble at the drilling :site responsible forgtheoperation ofthe release 'lleviclei i' i ffter Jthe vspring 4"13 has ergpanded in the releasing -aetior'ithevarius cvcjrnp'onents .ofthe mechanism are in 'thefollowing conditions. `Solenoid'27 deenergized-and tureA 26ans projected outwards. Arm 1:19 urged yfsprmg'fZZ-is in 4engager;rent"with an adjustable stop'35. 1Shoe"7'-"isinengagement'with stop v21fdue t0 the action of spring 13 and ,of .the cam surfaceiofvlplunger 8 `en- 'gfag'ingthe inclined surface 17'. To reset the mechafh'e fQllOWins predr is Ned1 t 3:2 1`iis1ota'te`dfin the direction 0f arrow F. The shaft '3,3 upon which KVthe ,leyerv34 is secured carries nle'ccentrically rnoun'ted'iroller which cooperates with "an internv formed-recess 37 Vin the Shoe .7, pivoting on the4 arns fr' 'rod S @to raise 'the .shoe indicated 'by arrow ig. lj), and to` produce movement toward the sigh; asia d atedvb'y arrow :fz (Fig 2). n wiu'be unde too`d tha Asuch ivrotation ofv shoe 7 and 4oftube 4 is anied by a Sliding displacement of the tube and h -m the direction foff'arrowlfi, by ,virtue of 4engagei t :f the inclined cam surface V17 with the slanting en lslirfacefoftheplunger8,'Vsothat 'the shoe is restored s initial position miwhich zit can engaged by latch member T18. Theforee t'bedevelop'ed *for'overconling the detent spring 13 is only moderate, as determineclby lFig. v2, acting "through the lspring 28. Y -sprngistwea-ker than spring `22, yet vwhen'compressed a carriage.

Athe Aangle 'of incline 17 `and'thefleverages used. `Crank 14S-on shaft 133 l.pulls `the end of the arm 19 upwardly in Although 4this suli'lcient amount it will overcome'the lattertolurgearm .19 in the .direction shown by arrow F', and towards the `endof the displacement of lever 34 a microswitch (not shown) is actuated in cooperation'with switch 12,to.re `energize the solenoid 27.

The spring 28 is necessaryrbecause the attractive .f orce of solenoid 27, while reaching a very high ivalue when the magnetic armatures 'are 1in engagement, `lsnevertheless insuilicient to overcome the action `OfspringZZ rand attract the :arm 19 when '-th'efmagnetic 'armatures :are

spaced apart, i-.e. when movable coreiarmature26Iisprojected out of the solenoid winding.

Thus lit is seen that the system described will instantaneously arrest the drill adva'ncing force assoonfasrthis force has exceeded predetermined limiting value. Itwill be understood that Vjust as'in .conventional safety release systems the pressure switch 12 may simultaneously control an electromagnetic clutch of 'the type'usually interposed between the feedmotorland lthe lead screw ofthe The system of the invention, however, in contrast to `such conventional systems, 'causes an'ins'tanftaneous backing-off of the 'drill tool `on occurrence of trouble. Breaking of the tool is thus averted and since the expansion of vspring 13 is nearly instantaneous, `full advantage is derived'from thevadditionalkinetic energy 4yielded at the'surface of the work as it drives back the fdrill due 'to 'the action of elastic stresses in the metal.

The additional accelerations that maybe developed'in such an elastic recoil ofthe drill are in a .range 'of "the order of from 30g to v40g (g vbeing the acceleration of gravity) and thus `enormously enhance the normal Vaccelerations that maybedue to a spring such as 13, which are of the order of Aonly 2g.

=Due 'to the helical motion of the drill rod relatively to the carriage, that is, rotatively and along its-axis Vthe vdetent latch l18 may be readily made to operate within the `permissible limits as dictatedby considerations of resist- -of vspring 22, all are preferably `made adjustable.` In

this way the mechanismlmaybe made to respond to any desired pressure surge 'transmitted'to capsule 10,that is,

Aany value of accidental increase in the drill thrust as determined by the nature ofthe work.

An initial bias may be applied to the vpressure capsule 10 by means ofthe lever '39, aided if necessary vby an insert shim 40, in order to take fup any inordinate rlost motion of thelplunger 8. Thus, assuming the pressure -uid used is to be compressed in a range extending from zero to a maximum pressure corresponding 'to a drill thrust of one ton, elastic compression of such Huid would result in a superfluous amount of `lost motion for 'plunger S. Preferably therefore, lever 39 is used to create A:an adjusted biasing force -somewhat lower Ythan the thrust corresponding to the particular metal being worked, soas to minimize the deformations inthe capsule -10 required to be developedtresulting from said thrustin service.

A`it will be understood that the particular mechanism described and illustrated may be modified in a wide variety of ways without exceeding the scope vof the invention as defined in the claims. i Y i' What I claim is:

1. In a drilling machine having a rwork carrierrotatable on an axis, a drill bar, a drill bar support, and .means Yfor axially feeding said support towards the work rin opposition to drilling freaction the combination therewith f means mounting 'the 'drill bar for limited helical die;

placement relative to the support, a pressure senser on ksaid support engaging the drill bar to sense said drilling reaction, a spring engaging the support and the drill bar and tending to displace the bar relative tothe support away from the work along an axial component of said helical displacement, a latch rotatably mounted on the support and engaging the drill bar to restrain the bar against a rotational component of said helical displacement, whereby the bar is blocked by the latch in an operative position in which said spring is stressed to bias said bar to apply pressure on said pressure senser, and means operatively connected with said pressure senser and to said latch to rotate the latch to a disengaging position in response to a predetermined drilling reaction vpressure sensed by the senser, whereupon the drlll bar is helically displaced to an idle position by said spring.

2. In a drilling machine the combination as claimed in claim l, wherein said latch engages said bar outwardly from the helical axis so that the drill bar tends to be pressed into engagement with the latch by a rotational component of said drilling reaction.

3. In a drilling machine having a work carrier rotatable on an axis, a drill bar, a drill bar support, and means for feeding the support and bar parallel to said axis towards the work in opposition to drilling reaction, the combination therewith of a lateral extension projecting from the bar and having a surface inclined to said axis, means mounting said bar and extension for limited axial and rotational displacement relative to the support upon an axis parallel to said work carrier axis, a pres- ,sure senser on said support including a mating inclined surface engaging said first surface, spring means urging `the bar away from the work relative to the support along an axial component of said displacement, a latch rotatably mounted on the support and engaging the bar to restrain it against a rotational component of said displacement, whereby the bar is blocked by the latch in an operative position in which said spring is stressed, and means operatively connected with said pressure senser and said latch to rotate the latch to a disengaging position in response to a predetermined drilling reaction sensed by the senser, whereupon the drill bar is axially and rotationally displaced by said spring means to an idle position.

4. In a drilling machine the combination as claimed in claim 3, wherein said latch in said engaging position thereof engages said bar outwardly from said axis and so as to oppose the rotational component of said displacement of the drill bar away from the work.

5. In a drilling machine the combination as claimed in claim 3, which comprises a second spring means urging said latch to its disengaging position, electromagnetic means operatively connected to said latch and having an energizingA circuit and adapted in a given condition of said circuit to rotate the latch to its engaging position in opposition to said second spring means, a switch connected in said circuit actuable to switch said circuit between said a given and another circuit condition, and an actuating connection from said pressure senser to said switch for actuating said switch for switching said circuit to said other circuit condition on a predetermined drilling reaction pressure being sensed by said pressure senser.

6. In a drilling machine the combination as claimed in claim 3, which comprises a second spring means urging said latch toits disengaging position, electromagnetic means operatively connected to said latch for holding said latch in its engaging position in opposition to said second spring means and actuable by said pressure senser to release said latch, whereupon said latch is moved to disengaging position by said second spring means, and resetting means for applying a rotational force to said bar for resetting said latch to its engaged condition after disengagement thereof, including means operated by said resetting means for reconditioning said electromagnetic means for operation.

7. In a machine tool or the like having a workpiece supporting member, a tool suporting member, and feeding means operatively connected to said members and operable to effect feeding movement of one relative to the other for feeding the tool and the workpiece in cutting engagement with each other, the combination therewith of a tool carrying element supported on said tool supporting member for movement thereof relative to said tool supporting member generally parallel to the feeding movement, a cam element supported on said tool supporting member for movement thereof in a predetermined line and provided with a surface inclined to said predetermined line of movement, a cam follower supported on said tool carrying element for concomitant movements thereof relative to said tool supporting member generally along said predetermined line and generally transversely of said predetermined line, said cam follower engaging said cam element to effect movement of said cam element in a given direction along said predetermined line upon movement of said cam follower in said given direction along said line, said cam follower being provided with a cam surface engaging said inclined surface of said cam element for effecting movement of said cam follower transversely of said line upon said movement of said cam follower in said given direction, and means operatively connecting said cam follower to said tool carrying element for effecting said movement of said tool carrying element relative to said tool carrying member to move the tool away from cutting engagement with the workpiece concomitantly with said movements of said cam follower upon the development of excessive resistance between the tool and the workpiece in the cutting operation.

8. In a machine tool or the like, the combination as defined in claim 7 which comprises means operatively connected to said cam element and to said feeding means and responsive to movement of said cam element along said predetermined line in said given direction for stopping said feeding movement upon said movement of said cam element.

9. In a machine tool or the like, the combination as dened in claim 7 which comprises a latch supported for movement thereof between a position out of engagement with said cam follower and a position engaging said cam follower to hold said cam follower against said movement thereof transversely of said predetermined line in `the direction away from engagement with said cam element inclined surface, means biasing said latch toward said position out of engagement with said cam follower, and means operatively connecting said cam element to said latch and operable for holding said latch against its `bias in -said cam follower engaging position and operable to effect movement of said latch under its bias toward said position out of engagement with said cam follower to release said cam follower for said movements thereof.

10. In a machine tool or the like the combination as defined in claim 9 which comprises manually operable means operatively connected to said latch and operable to effect movement of said latch away from said cam follower engaging position to release said cam follower and operable to move said latch into cam follower engaging position against said latch biasing means.

11. In a machine tool or the like the combination as defined in claim 9 in which said latch is provided by a lever pivotally supported on an axis extending transversely of said predetermined line, and a latch element carried by said lever outwardly from said pivotal axis generally in said direction transverse to said predetermined line and disposed on said lever so as to engage said cam follower in said engaging position of said latch to oppose said transverse movement of said cam follower.

12. In a machine tool or the like the combination as defined in claim 9 in which said means for holding said latch against its bias comprises electromagneticmeans operatively connected to said latch for effecting movement of said latch to cam follower engaging position in a given one of the two conditions of energization and deenergization of said electromagnetic means and for effecting movement of said latch away from cam follower engaging position under said bias in the other of said two conditions of energization and deenergization of said electromagnetic means, electrical control means connected to said electromagnetic means and operable to determine said conditions of energization and deenergization of said electromagnetic means, and means operatively connecting said cam element to said electrical control means for actuating said control means to determine upon movement of said cam element along said predetermined line in said given direction said other condition of said electromagnetic means for releasing said cam follower for movement thereof and of said tool carrying element to move the tool away from cutting engagement with said workpiece.

13. In a machine tool or the like, the combination as defined in claim 9 which comprises a shaft, means carried by said tool supporting member and supporting said shaft for rotation thereof on its axis, an eccentric carried by said shaft and engaging said cam follower upon rotation of said shaft for effecting movement of said cam follower in said given direction into engagement with said cam element generally along said predetermined line and concomitant movement of said cam follower transversely of said line under the camming action of said inclined surface of said cam element, and manually operable means connected to said shaft for effecting said rotation thereof.

14. In a machine tool or the like having a workpiece supporting member rotatable on an axis, a tool supporting member supported for movement thereof generally along said axis toward and away from the workpiece, and feeding means operatively connected to said tool supporting member and operable to effect movement of said tool supporting member for feeding the tool in cutting engagement with the workpiece, the combination therewith of a tool carrying element supported on said tool supporting member for limited movement of said tool carrying element relative to said tool supporting member generally along said axis and rotationally on said axis, a cam element supported on said tool supporting member for movement thereof in a predetermined line generally along said axis and provided with a surface inclined to said predetermined line of movement, a cam follower supported on said tool carrying element for concomitant movements thereof with said tool carrying element relative to said tool supporting member generally on said axis of rotation of said workpiece supporting member, said cam follower engaging said cam element to effect movement of said cam element in a given direction along said predetermined line upon movement of said cam follower in said given direction along said axis, said cam follower being provided with a cam surface engaging said inclined surface of said cam element for effecting rotational movement of said cam follower and of said tool carrying element on said axis upon movement of said cam follower in said given direction along said line, a latch supported for movement thereof between a position out of engagement with said cam follower and a position engaging said cam follower, said latch in said cam follower engaging position being disposed so as to resist said rotational movement of said cam follower and of said tool carrying element on said axis tending to be produced by said workpiece in the rotation thereof, said cam follower thereby being confined during engagement of said latch for said movement thereof with said tool carrying element in said given direction along said predetermined line so as to move said cam element in said given direction along said line upon development of excessive resistance between said tool and the workpiece along said axis in the cutting operation, means operatively connected to said cam element and to said latch and responsive to movement of said cam element along said predetermined line in said given direction for moving said latch to said position out of engagement with said follower, said cam follower and said tool carrying element under the camming action of said inclined surface of said cam element engaging said cam surface of said cam follower then being rotated on said axis in the direction rotatably to move said tool away from the workpiece.

15. In a machine tool or the like having a workpiece supporting member, a tool supporting member, and feeding means operatively connected to said members and operable to effect feeding movement of one relative to the other for feeding the tool and the workpiece in cutting engagement with each other, the combination therewith of a tool carrying element supported on said tool supporting member for limited movement of said element relative to said tool supporting member generally along the line of the relative feeding movement, means responsive to the pressure developed between the workpiece and the tool along said line of feeding movement and providing a continuous operative connection between said tool carrying element and said tool supporting member for effecting said limited relative movement of said tool carrying element and said tool supporting member along said line in the direction to move the tool away from the workpiece in response to a predetermined pressure between the workpiece and the tool along said line of feeding movement.

16. In a machine tool or the like the combination as defined in claim 15 which comprises means biasing said tool carrying element to move relative to said tool supporting member in said direction to move the tool away from the workpiece, means movable between a position in which it engages said tool carrying element and a position disengaged from said tool carrying element, and means cooperating with said movable means in said element engaging position to restrain said tool carrying element against said movement thereof under its bias, said biasing means in the disengaged position of said movable means effecting said movement of said tool carrying element relative to said tool supporting member in the direction to move the tool away from the workpiece.

References Cited in the file of this patent UNITED STATES PATENTS 2,418,220 Churchill Apr. l, 1947 

